1. Field of the Invention
This invention relates to a method for producing high strength copper alloy having excellent fatigue property, and heat-resistance property as well as favorable shaping property, hence it is suitable as the material for manufacturing electronic parts of wide varieties such as switches, relays, connectors, and so forth.
2. Discussion of Background
Heretofore, for the abovementioned electronic parts, beryllium copper (JIS C1720) and phosphor bronze (JIS C5210, C5191, and others) have been much used.
Since beryllium copper has high mechanical strength, excellent fatigue property, and a relatively favorable heat-resistant property, it has been used as the material for manufacturing high quality springs. On the other hand, phosphor bronze has been used widely as the material for general purpose springs, since it has inferior performance than those of beryllium copper.
However, beryllium copper has its disadvantage in that beryllium (Be) as the principal component for the alloy is very expensive, hence such expensive alloy component would inevitably reflect on the manufacturing cost of the product. On the other hand, phosphor bronze is considerably inferior to beryllium copper in respect of its fatigue property and other mechanical properties, even though it is relatively cheaper than beryllium copper.
The alloy according to the present invention composed of Cu-Ni Sn as the basic components is highlighted as the age-hardening alloy of spinodal decomposition type having high mechanical strength On account of its superiority in its static strength, the alloy has been used widely in the field of electronic parts as represented by connectors, etc.. In respect of its fatigue property, however, the alloy was at a level not so much different from the conventional phosphor bronze, hence it was not necessarily suitable as the material for various mechanical parts represented by switches, relays, etc., on which repreated stress is imposed.
The present inventor proposed in Japanese Patent Application No. 100793/1987 a method for heat-treatment, by which the abovementioned fatigue property is remarkably improved. While the fatigue property could be improved with great stride, however, there arose considerable decrease in respect of its shaping property and static strength with the consequent inability to have its excellent properties in every aspect of its properties.